1. Field of the Invention
The present invention relates to a wire bonding device used for manufacturing a semiconductor integrated circuit device.
2. Description of the Prior Art
One typical arrangement of a conventional hybrid integrated circuit device among semiconductor integrated circuit devices is that a semiconductor chip is mounted on a ceramic substrate or a glass reinforced epoxy substrate, and the semiconductor chip is connected to a wiring part of the substrate by wire-bonding the substrate wiring part to the semiconductor chip.
The description will hereinafter deal with steps of wire bonding. To start with, a metal wire is inserted through a hollow capillary, and a tip of the metal wire is slightly protruded from the capillary top. The protrusion of the metal wire from the top of the capillary is so fused by electric discharge as to assume a ball-like configuration. The ball-like tip of the metal wire, which is protruded from the capillary top, pushes this capillary top against a bonding face of the semiconductor chip. Ultrasonic vibrations are applied to the capillary, while the capillary top remains pushed against the bonding face of the semiconductor chip. Thereupon, the protruded metal wire from the capillary top is fused by frictional heat with the semiconductor chip and is thereby joined thereto. In this state, the capillary is temporarily raised and moved above the wiring part of the substrate. Subsequently, the capillary is depressed on the wiring part of the substrate, and the capillary again undergoes the ultrasonic vibrations. The protruded metal wire from the capillary top is immediately fused by the frictional heat with the substrate wiring part, thus connecting the semiconductor chip to the substrate wiring part. Next, the capillary is raised from the substrate wiring part, and the protruded metal wire from the capillary top is cut off. Then, the protruded metal wire from the capillary top is fused by the electric discharge so that the tip of the metal wire assumes the ball-like shape. The semiconductor chip is connected to the substrate wiring part by repeating the above-described operations.
During such operations, a load caused when the capillary pushes the metal wire against the bonding face exerts a large influence on a bonding quality. For instance, if the pushing load is excessively large, the ball-shaped tip of the metal wire is greatly deformed, with the result that the tip thereof contacts the contiguous portion and is short-circuited in some cases. The bonding face of the semiconductor chip is probably defaced. Whereas if the pushing load is too small, the metal wire often comes off the bonding part because of insufficient bonding.
On the other hand, if a warp can be seen in the substrate or there is variance of thickness thereof, when the capillary is pushed against the bonding face after moving it up and down at a given distance, there is produced wide variations in the pushing load of the capillary.
Under such circumstances, in the prior art wire bonding device, the capillary temporarily ceases to descend while being in contact with the bonding face, and thereafter the capillary is pushed against the bonding face by a predetermined force.
There arises, however, a problem inherent in the conventional wire bonding device, wherein it takes much time to effect a series of operations, because the capillary temporarily stops lowering while contacting the bonding face and is then pushed against the bonding face by the predetermined force.